Extrapolated across the whole of England, these rough figures would mean almost 1 million people objecting to NHS record sharing - although it is likely the final figures could be higher with the increased publicity surrounding the full rollout.

In a written response to Labour health minister Jamie Reed MP, Mr Freeman said: ‘July 2015 figures covering 61% of the care.data pathfinder general practitioner (GP) practices suggest that, across those practices, 1.8% of patients have registered a type 1 objection, to their identifiable data being shared outside their GP practice for purposes other than their direct care.

‘Some practices have higher volumes of objections than others, but the majority fall within 0.5-2.5% range.’

Phil Booth, coordinator of privacy advocacy group medConfidential, pointed to the response rate from the pilot practices - 60% of whom provided figures.

He said: ‘It’s interesting to note that, though they are talking to “enthusiast” GP practices, it appears almost 40% of them have not reported the number of their patients who have opted out.

‘We suspect the pattern of opt-outs will vary across the country and – because so few practices have volunteered in Leeds – the majority of the data that Mr Freeman is referring to will be from “rural” areas. This may also have an impact on the figures.

‘The 2.5% in his answer is not an upper limit – it is simply the upper end of a range that Mr Freeman describes as “the majority”.’